With the increasing development and consumption of mobile devices, electric vehicles, hybrid vehicles, power storage systems, uninterrupted power supplies, or the like, the consumption of secondary batteries as energy sources are rapidly increasing as well as its various forms thereof. Therefore, batteries are being studied very actively to cope with such diverse demands.
A secondary battery is a device that stores electrical energy supplied from an external source in a chemical form, and when needed, converts chemical energy to electrical energy. In the sense of being recharged many times, a secondary battery is also referred to as a rechargeable battery. Common secondary batteries include a lead storage battery, a Ni—Cd battery, a Ni-MH storage battery, a Li-ion battery, a Li-ion polymer battery, and the like. When compared to a disposable primary battery, not only is a secondary battery more economically efficient, it is also more environmentally friendly.
A majority of secondary batteries being currently used are cylindrical, prismatic, or pouch-type secondary batteries. These secondary batteries are classified into a pouch-type secondary battery, a cylindrical secondary battery, and a prismatic secondary battery based on a type of an outer case. Because secondary batteries are manufactured by mounting an electrode assembly including an anode, a cathode, and a separator in a cylindrical or prismatic metal case or a pouch-shaped case of an aluminum laminate sheet, and injecting an electrolyte into the electrode assembly, they have advantages of easy manufacturing and a low manufacturing cost. However, where a predetermined mounting space is necessarily required, secondary batteries have a disadvantage of limited shape adaptation. As a result, the cylindrical, prismatic or pouch shape of the secondary batteries is a limitation in developing various shapes of mobile devices. Accordingly, there is a need for a new type of secondary battery that is easily adaptable in shape.
To fulfill this need, suggestions have been made to develop a cable-type secondary battery having a very high ratio of length to cross-sectional diameter. Korean Patent Application publication No. 2005-99903 discloses an adaptable battery consisting of an inner electrode, an outer electrode, and an electrolyte layer interposed therebetween. However, such secondary battery has an elongated shape, and thus, mainly features a so-called cable structure whereby the secondary battery is able to stretch and retract in a lengthwise direction.
Meanwhile, studies are being actively made on a connection terminal to connect a cable-type secondary battery to a device to supply power or connect to a charger to receive a charging power.